1. Technical Field of the Invention
The present invention generally relates to communications networks. More particularly, and not by way of any limitation, the present invention is directed to a loop prevention system and method for use with a stackable Ethernet switch system.
2. Description of Related Art
In data communication networks based on the Ethernet technology, packet switches, including multi-layer switches and routers, are used to operatively couple many nodes for purposes of communicating packets of information therebetween. Switches that are made to stand alone without relying on a shared backplane have a plurality of ports and an internal switching fabric for directing inbound packets received at an ingress port to a suitable egress port. In some implementations in the art, the switching capacity is enhanced by linking a plurality of stand-alone switches by operatively linking selected ports (i.e., stack ports) of the switches together so as to create a stackable switch system operable as a single switching entity. Such systems, sometimes called stack switch systems, are often employed together at a customer's premises, e.g., an enterprise.
In a typical implementation, a system of stack switches are operatively interconnected via a pair of designated stack ports present on each switch, also referred to as an element. The system of stack switches is generally coupled in series and the topology of the system is generally characterized by a closed loop called a ring or an open strand of switches referred to herein as a chain. Each of the stack switches is adapted to perform switching between its own data ports as well as the data ports of other stack switches by transmitting packets via the stack ports using stack switch identifiers that facilitate the efficient transmission and switching of these packets to the appropriate stack switch element.
It is known that in certain architectures involving stackable switch elements, looping of user data traffic may occur when the control processor of one of the switch elements becomes dysfunctional. Once a loop in the network is created, the network becomes unusable and requires user intervention to troubleshoot the problem, thereby leading to network downtime and associated inefficiencies.